law of cosines again ...
Study this web page.
You can work out this problem from the given.
With pencil and paper! We're not saying that you should draw a picture here so that we can understand it, we are saying that you should draw a picture so you can understand it. You don't see that you will have an iscosceles triangle with two sides of length 21 and base of length 32? And you are asked to find the measure of the 'vertex' angle- the one opposite the side of length 32. As skeeter suggested initially, use the cosine law. Do you know what that is?